The background description provided herein is for the purpose of generally presenting the context of the disclosure. Unless otherwise indicated herein, the materials described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
Typically, during the startup of a virtual machine (VM), the guest operating system (OS) of the VM first boots the virtual Boot Strapping Processor (BSP) of the VM, which in turn, sequentially boots all virtual Application Processors (AP) of the VM in a specified order. For Intel x86 execution environment, the virtual BSP (hereinafter, simply BSP) sends an INIT-SIPI-SIPI IPI sequence to start the virtual AP (hereinafter, simply AP). Each woken AP will begin execution in x86 real mode, and later switches into a protected mode, e.g., a 32-bit protected mode. Accordingly, the virtual machine monitor (VMM) (also referred to as hypervisor) is required to support real mode execution during AP startup, which increases the complexity of the VMM. (INIT=Initialization, IPI=Inter-Processor Interrupt, SIPI=Startup IPI.)